Shotgun sports date back to the late 1700's with the introduction of trap shooting of live pigeons. The sport later evolved with the introduction of clay pigeons in 1880 and the development of reliable clay throwing machines in 1890. The two main types of shotgunning games that evolved are Trap and Skeet. Trap is a game where the clays are thrown from a single location or house, at different random angles while the shooters rotate between five shooting positions. Skeet is a game where clays are thrown from two locations or houses, at consistent trajectories while shooters rotate between eight stations. International trap was introduced as an Olympic Sport in 1952, while International Skeet was introduced as an Olympic Sport in 1968. In Sporting Clays, a third shotgunning game which has been introduced in recent years, clays are thrown from many locations in an attempt to resemble a real life hunt, while shooters walk through a golf course-like field.
All shotgun sports require the shooter to accurately predict the trajectory of the target. This requires a good understanding of the physics involved, including the speed of the shot and target, the trajectory of the shot and target, the type of shot and the size of the target. To complicate things, shooters need to develop the ability to predict the position of the target and aim their weapons appropriately so that the shot intersects the target. This drives the need to shoot the clay by leading it. The lead is defined as the distance in front of the target, which the shooter aims and shoots at in order to break the target. This lead will vary depending on the game, targer speed, shot type, shot speed, shooters technique, and atmospheric conditions; it can range from a few inches to more than ten feet.
The greatest challenge in shotgunning sports is mastering the lead. The supersonic nature of the shot, with speeds ranging from approximately 1100 to 1400 ft/s (335 to 427 m/s), and the speed of the target, ranging from approximately 40 to 70 miles/h (64 to 112 Km/h), make it almost impossible for the shooter to know where his shot should go relative to the target. To further complicate accurate aiming, the human brain and eye refresh images approximately every 0.1 seconds, while the average shot flight time to the target is approximately 0.05 seconds. This makes the game a real challenge to learn, and very difficult and time-consuming to master.
The visibility of an object to the human eye generally depends on the size of the object, the relative distance between the object and the observer, the relative speed of the object, the color of the object, and the light intensity and atmospheric conditions. Inventors have developed tracers for shotgun shells in an attempt to aid the shooter in visualizing his or her shot with regard to the target.
Prior tracers can be categorized as non-ignition and ignition type. Non-ignition type inventions have been unsuccessful in the shooters market; they include:                (a) Pellet with fluorescent tails (U.S. Pat. No. 3,760,735 to P. F. Schmitt in 1971);        (b) Shot encapsulated with light reflective coating (U.S. Pat. No. 4,080,899 to W. L. Luban in 1978);        (c) Chemiluminescent tracer that accompanies the shot (U.S. Pat. No. 4,553,481 to V. Ricci in 1984); and        (d) Shotgun shell flight path indicator (U.S. Pat. No. 6,539,873 to E. W. Diller in 2003).        
Ignition type inventions although promising have had very limited success in the market place, these include:                (a) Single bullet-shaped tracer projectile with pyrotechnic mixture in the trailing end (U.S. Pat. No. 3,405,638 to J. A. Stoner in 1968);        (b) Shot pellets coated with ignitable illuminant or smoking agent (U.S. Pat. No. 4,389,939 to H. Ofuji in 1983);        (c) Single ball-shaped tracer projectile with pyrotechnic mixture in the trailing end (U.S. Pat. No. 4,841,866 to D. W. Miesner in 1989); and        (d) Tracer cartridges (U.S. Pat. No. 5,429,054 to R. E. Topping in 1995).        
The ignition type designs available today are mostly derived from U.S. Pat. No. 3,406,648 and U.S. Pat. No. 4,841,866. The marginal success of these inventions can be attributed to the high price charged and the clear fact that these inventions do not function properly. Currently available tracers, while visible, do not provide the shooter with a consistent reference to improve his or her shooting. Typical reasons tracers fail include the following:                (a) The tracer does not have a flight pattern consistent with that of the shot and therefore fails to provide the shooter with an appropriate reference.        (b) The tracer fails to ignite consistently because the pyrotechnic material does not have enough time and surface area to absorb heat from the propellant blast as it separates from the shot cup.        (c) Current tracer inventions have limited, if any, applicability to smaller shotgun gauges because of the geometric constraints in the smaller gauges like 16, 20, 28, and 410.        
More specifically, currently available tracers fail because the tracer projectile travels randomly with the shot pattern. Manufacturers claim that the tracer projectile travels in the middle of the shot pattern, but field tests prove otherwise. The point of impact at 22 yards of currently available tracer projectiles is no more predictable than any single pellet within the shot. Field tests indicate that currently available tracers provide 30 to 40 inch groups from the point of aim, even though shotgun sports require a 12 inch group, or better, to be effective. The inaccuracy of current tracer designs stems from the fact that the tracer projectile is located at the bottom of the shot cup. Once fired, the tracer is subjected to the chaotic behavior and interference of the supersonic gases, shot and wad as it leaves the barrel and travels to the target. These interferences present the greatest challenge in designing an effective shotgun tracer. An improved tracer design should address these interferences and should still be capable of carrying the proper amount of shot within the constraints of standard shotgun cartridges.